Initial revision

1 files changed, 114 insertions, 0 deletions

diff --git a/src/atiutil.c b/src/atiutil.c
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+/* $XFree86: xc/programs/Xserver/hw/xfree86/drivers/ati/atiutil.c,v 1.8 2003/01/01 19:16:34 tsi Exp $ */
+/*
+ * Copyright 1997 through 2003 by Marc Aurele La France (TSI @ UQV), tsi@xfree86.org
+ *
+ * Permission to use, copy, modify, distribute, and sell this software and its
+ * documentation for any purpose is hereby granted without fee, provided that
+ * the above copyright notice appear in all copies and that both that copyright
+ * notice and this permission notice appear in supporting documentation, and
+ * that the name of Marc Aurele La France not be used in advertising or
+ * publicity pertaining to distribution of the software without specific,
+ * written prior permission.  Marc Aurele La France makes no representations
+ * about the suitability of this software for any purpose.  It is provided
+ * "as-is" without express or implied warranty.
+ *
+ * MARC AURELE LA FRANCE DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
+ * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS.  IN NO
+ * EVENT SHALL MARC AURELE LA FRANCE BE LIABLE FOR ANY SPECIAL, INDIRECT OR
+ * CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE,
+ * DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
+ * TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
+ * PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include "atiutil.h"
+
+/*
+ * ATIReduceRatio --
+ *
+ * Reduce a fraction by factoring out the largest common divider of the
+ * fraction's numerator and denominator.
+ */
+void
+ATIReduceRatio
+(
+    int *Numerator,
+    int *Denominator
+)
+{
+    int Multiplier, Divider, Remainder;
+
+    Multiplier = *Numerator;
+    Divider = *Denominator;
+
+    while ((Remainder = Multiplier % Divider))
+    {
+        Multiplier = Divider;
+        Divider = Remainder;
+    }
+
+    *Numerator /= Divider;
+    *Denominator /= Divider;
+}
+
+/*
+ * ATIDivide --
+ *
+ * Using integer arithmetic and avoiding overflows, this function finds the
+ * rounded integer that best approximates
+ *
+ *         Numerator      Shift
+ *        ----------- * 2
+ *        Denominator
+ *
+ * using the specified rounding (floor (<0), nearest (=0) or ceiling (>0)).
+ */
+int
+ATIDivide
+(
+    int       Numerator,
+    int       Denominator,
+    int       Shift,
+    const int RoundingKind
+)
+{
+    int Rounding = 0;                           /* Default to floor */
+
+#define MaxInt ((int)((unsigned int)(-1) >> 2))
+
+    ATIReduceRatio(&Numerator, &Denominator);
+
+    /* Deal with left shifts but try to keep the denominator even */
+    if (Denominator & 1)
+    {
+        if (Denominator <= MaxInt)
+        {
+            Denominator <<= 1;
+            Shift++;
+        }
+    }
+    else while ((Shift > 0) && !(Denominator & 3))
+    {
+        Denominator >>= 1;
+        Shift--;
+    }
+
+    /* Deal with right shifts */
+    while (Shift < 0)
+    {
+        if ((Numerator & 1) && (Denominator <= MaxInt))
+            Denominator <<= 1;
+        else
+            Numerator >>= 1;
+
+        Shift++;
+    }
+
+    if (!RoundingKind)                          /* Nearest */
+        Rounding = Denominator >> 1;
+    else if (RoundingKind > 0)                  /* Ceiling */
+        Rounding = Denominator - 1;
+
+    return ((Numerator / Denominator) << Shift) +
+            ((((Numerator % Denominator) << Shift) + Rounding) / Denominator);
+}